Researchers at Washington University School of Medicine (WUSTL; St. Louis, MO, USA) and 117 hospitals across the United States followed 352 postmenopausal women who were diagnosed with estrogen-receptor positive (ER+) breast tumors. Participants were placed in one of three groups: marginal, meaning breast-conservation surgery was possible but likely to be disfiguring or to require several surgical procedures; mastectomy-only, meaning breast-conservation surgery was not possible; and inoperable, meaning mastectomy would not completely remove the cancer. The study participants were then randomly assigned to receive one of three estrogen-lowering agents: exemestane (25 mg daily), letrozole (2.5 mg daily), or anastrozole (1 mg daily). The participants received aromatase inhibitor therapy for 16 weeks before surgery for breast cancer, and the extent of their tumors was monitored both before and after the drug treatment.
Following the aromatase inhibitor therapy, the women were reevaluated to see which surgical option was appropriate for them. The results showed that in 82% of women in the marginal group, 51% percent of the women in the mastectomy-only group, and 75% of the women in the inoperable group the tumors had shrunk to an extent that allowed for successful breast-conservation surgery instead of mastectomy. No statistically significant difference in effectiveness was found among the three drugs administered. The study findings were presented at the annual meeting of the American Society of Clinical Oncology (ASCO), held during June 2010 in Chicago (IL, USA).
"ER+ breast cancer can be thought of as a chronic disease because patients generally take estrogen-lowering agents for many years after surgery to repress recurrence,” said study presenter and coauthor Matthew Ellis, M.D., Ph.D., of WUSTL. "In other chronic diseases, such as hypertension or diabetes, a patient's response to treatment is continually monitored. But we've never done that with breast cancer. By treating breast cancer patients with estrogen-lowering drugs for three or four months before surgery, we can monitor treatment response and then specifically tailor surgical and postsurgical treatment based on this response.”
Aromatase inhibitors work by inhibiting aromatization, an enzymatic process, which converts androgens into estrogens. As breast tissue is stimulated by estrogens, decreasing their production is a way of suppressing recurrence of the breast tumor tissue. Aromatase inhibitors are generally not used to treat breast cancer in premenopausal women.
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